Referral to hematology for anemia is common. In paroxysmal nocturnal hemoglobinuria (PNH), cells deficient in the glycosylphosphatidyl inositol (GPI) anchor are lysed by complement. Eculizumab improves overall survival and quality of life while reducing hemolysis, transfusion requirements, and thrombosis. We evaluated the frequency of screening for PNH in patients with unexplained anemia. Key clinical features, laboratory data, and investigations were recorded for patients referred for anemia since 2010, without a specific cause found. PNH testing was done by flow cytometry. 540 patients had: anemia not yet diagnosed (NYD, n=318 (including unexplained iron deficiency, n=92; DAT-negative hemolysis, n=9)); anemia of chronic disease, n=173; and pancytopenia NYD, n=49. 82.4% had LDH testing done; 85.0% total bilirubin; 78.7% reticulocyte counts; and 40.6% haptoglobin level; 131 (24.2%) had possible hemolysis. PNH testing was done in 56 (10.4%). Those screened for PNH were more likely to have: younger age (P=0.04); a history of thrombosis (P<0.001); undergone a BMBx (P<0.001); received RBC transfusions (P=0.0018); or evidence of DAT-negative hemolysis (P<0.001). In summary, PNH was tested for in a minority of patients with unexplained anemia (10.4%) despite potential indicators of hemolysis in 24.2%. Increased screening could identify patients who would benefit from treatment and should be considered.